fatty acid synthesis/degradation
Terms
undefined, object
copy deck
- what is the first step in getting energy from fatty acids
- FREE the fatty acid from lipids.
- what is major type of lipid fatty acids stored in
- Triacylglycerols in adipose tissue
- What are the three phases of lipid catabolism?
-
1: fatty acid mobilization (STAGE 1)
2. fatty acid activation (STAGE 1)
3. fatty acid oxidation (STAGE 2/3) - What are the three STAGES of lipid catabolism
-
Stage 1. Mobilization/activation of fatty acids
Stage 2: F.A. Oxidation to Acetyl CoA
Stage 3: Acetyl CoA oxidation via CAC - how many acetyl CoA's are produced per TAG?
- number of carbons/2
-
How are F.A./TAG's freed from adipose cells?
what enzyme? -
Break down TAG into glycerol and fatty acids, one at a time.
lipoase -
how is lipase activated?
what does it do? -
by hormonal regulation (glucagon, epinephrine, norepin, ACTH
hydrolyzes TAG's into glycerol + fatty acids. - how is lipase inhibited?
- by insulin; insulin says STORE what you just ate as energy. so you don't want to break down TAG's.
-
Step 2 in fatty acid catabolism:
activation? how many steps? -
-transfer fatty acid to CoA. two steps:
1. Hydrolysis of ATP to form phosphoester bond (fatty acid bound to AMP) and PPi. (acyl adenylate)
2. Break phosphoester bond and form thioester bond - gives acyl CoA + AMP - where does fatty acid activation take place?
- in cytoplasm
- what enzyme catalyzes F.A. activation (both steps)?
- Acyl CoA synthetase
- what are the two products of fatty acid degradation?
-
Activated acyl group
activated acetyl group -
what are the f.a. metabolism enzymes
oxidation
hydration
oxidation
cleavage(thiolysis) -
1. acyl coA dehydrogenase
2. enoyl coA hydratase
3. hydroxyacyl coA dehydrogenase
4. beta-ketothiolase - what is ATP yield per molecule of palmitate
- 106
-
what is yield per palmitate?
-coA
-NADH
-FADH2
how many ATP used -
8
7
7
2 for activation - what gives more ATP per gram, and how much more than the other: fat or glucose
- FAT: gives 2.5 times as much ATP per gram of fat than gram of glucose.
-
What is the first step of F.A. syntheis?
enzyme? -
Activation of Acetyl Co-A - commitment to f.a. synthesis.
CARBOXYLATION - gives malonyl CoA.
enzyme: acetyl coA Carboxylase - what significant thing is required to start f.a. synthesis?
- ATP cleavage to ADP + Pi.
- what is significant about acetyl CoA carboxylase?
- -It is allosteric; affected by hormones.
- Significant differences between f.a. synthesis/degradation:
-
-ACP versus CoA
-Reductions use NADPH (synth) vs. NAD+ for oxidation (degrad) - Difference between bacterial/mammalian fatty acid synthesis:
- Enzyme - complex vs. free enzymes.
- what is the similarity between ACP and Coenzyme A?
- both have a phosphathiene arm, but CoA has an ADP where ACP has a protein so it's a macro CoA
- what transfers acetyl and malonyl from CoA to ACP?
- transacylases.
- General Fatty Acid Synthase characteristics to know:
-
-Homodimer
-7 active sites
-one single polypeptide chain -
Domain 1:
AT
MT
CE -
Acyl transferase
Malonyl Transferase
Condensing Enzyme
All on D1 of fatty acid synthase -
All on Domain 2
KR
DH
ER
ACP -
keto reductase
dehydrogenase
enoyl reductase
acyl carrier protein
all on domain 2 of f.a. synthase - How does fatty acid synthase work?
-
Malonyl CoA transfers from MT to ACP
Acetyl CoA transfers from AT to CE.
The two condense; then reduction at 3 other sites. Then transfer elongated f.a. to CE, ready for antother round.